Polyester resin composition with a long shelf life

ABSTRACT

UNCURED, CURABLE, UNSATURATED POLYESTER RESIN COMPOSITIONS CONSISTING ESSENTIALLY OF AN UNSATURATED POLYESTER, AN ETHYLENICALLY UNSATURATED MONOMER SUCH AS STYRENE OR A SIMILAR MONOMER INHIBITED WITH ABOUT 0.1-1.5 MOLE PERCENT OF 4,6-DINITRO-O-CRESOL OR 2,4-DINITROANILINE HAVING SHELF LIVES IN EXCESS OF ABOUT 100 DAYS AT ABOUT 70*C.

United States Patent O US. Cl. 260-864 8 Claims ABSTRACT OF THEDISCLOSURE Uncured, curable, unsaturated polyester resin compositionsconsisting essentially of an unsaturated polyester, an ethylenicallyunsaturated monomer such as styrene or a similar monomer inhibited withabout 0.1-1.5 mole percent of 4,6-dinitro-o-cresol or 2,4-dinitroanilinehaving shelf lives in excess of about 100 days at about 70 C.

CROSS REFERENCE TO RELATED APPLICATION This is a continuation-in-part ofour copending application Serial No. 782,750, filed Dec. 10, 1968, andnow abandoned.

BACKGROUND OF THE INVENTION The invention described and claimed hereinwas made in the course of or under a contract or subcontract thereunderwith the Department of the Air Force, Department of Defense.

This invention is in the field of stabilized, uncured polyester resincompositions which are liquids at room temperature (e.g., ca. 15-35 C.).More particularly, this invention is in the field of stabilized,uncured, curable burn resistant, unsaturated polyester resincompositions, said compositions comprising about 10-45% (or about20-40%) by weight of monomeric styrene (or similar ethylenicallyunsaturated monomer), about 0.1-1.5 mole percent (as hereinafterdefined) of an inhibitor selected from a group consisting of4,6-dinitro-o-cresol and 2,4- dinitroaniline, and enough uncured,unsaturated polyester to total 100% by weight, said compositions being aliquid at room temperature and having a shelf life (gel time) in excessof about 100 days at about 70 C. and in excess of about 2,500 days atabout 25 C.

Although an extended shelf life at elevated temperature (e.g., a geltime in excess of about 20-30 days at 70 C.) is generally unnecessary inthe uncured, curable, burn resistant, unsaturated polyester resincompositions used commercially in North America and Europe, the extendedshelf life of the polyester resin compositions of this invention isespecially valuable in relatively undeveloped tropical and desert areassince polyester resin compositions shipped to such areas can be storedfor several weeks on open docks, in fields, or in sheds (which lack airconditioning facilities) under conditions such that the temperature mayreach about 50-65? C. The compositions of this invention are especiallyuseful for constructing quick-curing pads for use as runways for lightaircraft and for constructing quick curing slabs to support houses,office buildings, storage sheds, and the like in primitive areas.

U.S. Pat. 2,779,701 (Robitschek et al., 154/43) teaches (lines 49-51 ofcolumn 14) that polymerization inhibitors (stabilizers) usuallyconstitute about 0.001-1% by weight of flame-retardant polyestercompositions. US. Pat. 3,288,735 (Watanabe et al., 260/ 17.4) presents alist of inhibitors including hydroquinone, trinitrophenol,4-ethylcatechol, 3-pheny1catechol, and 3-isobutylcatechol which havebeen used to increase the gel time (shelf life) of unsaturated polyesterresin compositions.

3,737,480 Patented June 5, 1973 ice Mondvai et a1. (Magyar KemiaiFolyoriat 1967, 73, 350) teach that certain nitrophenols inhibit thepolymerization of methylmethacrylate and Lang (J. Chem. Eng. Data 1960,5 (No. 1), 53) teaches that certain nitropheuols inhibit thepolymerization of certain substituted styrenes.

US. Pat. 3,092,609 (Kostelitz et al., 260/459) presents data which, showthat the stabilization of polymer systems is an empirical art notadapted to prediction by those skilled in said art. In other words, saiddata show that one should test a compound to determine its elficiency(or lack thereof) as an inhibitor to increase shelf life of a liquidsystem which can be cured to form a solid system.

Stabilized, uncured, curable, burn resistant, unsaturated, liquid (atroom temperature) polyester composition comprising about 10-45% byweight of monomeric styrene (or similar ethylenically unsaturatedmonomer) and about 0.001-l% by weight of inhibitor and enough uncured,curable, unsaturated polyester to total are well known in the art.However, the prior art compositions diifer from the compositions of thisinvention in; (a) the nature (chemical identity) of stabilizer(inhibitor or gel retarder) present; and (b) shelf life (gel time)-thegel time of the prior art resins being about 15-50 days or less at about70 C.

SUMMARY OF THE INVENTION In summary, our invention is a stabilized,uncured, curable, burn resistant, unsaturated polyester resincomposition consisting essentially of;

(a) An unsaturated polyester of; (i) a polyhydric alcohol selected froma first group consisting of ethylene glycol, diethylene glycol,propylene glycol, and a polyethylene glycol having a molecular weightbetween 300 and 4000; (ii) a member selected from a second groupconsisting of chlorendic acid and chlorendic anhydride; (iii) a memberselected from a third group consisting of maleic acid, fumaric acid,itaconic acid, and aconitic acid or an anhydride of the third groupmember; and (iv) a member selected from a fourth group consisting oftricarballyic acid, citric acid, succinic acid, adipic acid, sebacicacid, azelaic acid, phthalic acid, and terephthalic acid or an anhydrideof the fourth group member, the chlorine content of the stabilizedpolyester resin composition being 20 to 30%, the mole ratio of the thirdgroup member to the fourth group member being 1:0.25-12;

(b) An ethylenically unsaturated monomer selected from a fifth groupconsisting of styrene, vinyl toluene, ozmethylstyrene, dimethylstyrene,the methyl-u-methylstyrenes, a-bromostyrene, B-bromostyrene, a-ChlOIO-styrene, B-chlorostyrene, diallylphthalate, vinylacetate, methylmethacrylate, and divinylbenzene, the fifth group member constitutingabout 10-45% (preferably about 20-40%) of the stabilized, uncurred,curable, burn resistant, unsaturated polyester resin composition; and

(c) An inhibitor selected from a sixth group consisting of4,6-dinitro-o-cresol and 2,4-dinitroaniline, the sixth group memberbeing present in an amount between about 0.1 and 1.5 mole percent basedon the stabilized, uncured, curable, burn resistant, unsaturatedpolyester resin composition, said composition having a gel time of atleast about 100 days at 70 C.

DESCRIPTION OF PREFERRED EMBODIMENTS rendic anhydride) and thecomposition has a bromine 3 content of about -12% (rather than achlorine content of about 2030% In other preferred embodiments of thecompositions of; (a) the above Summary; or (b) Embodiment A, supra:

(l) The sixth group member is present in an amount between about 0.25and about 1 mole percent based on the stabilized, uncured, curable, burnresistant, unsaturated polyester resin composition;

(2) About 0.030.5 mole percent of cobalt, calculated as Co, is presentin the stabilized, uncured, curable, burn resistant, unsaturatedpolyester resin composition, the cobalt being added as a soluble cobaltsalt or as an adduct of such cobalt salt and a member selected from thesixth group, the mole ratio of cobaltzsixth group member in said adductbeing about 1:1; and

(3) The fifth group member is styrene.

DETAILED DESCRIPTION OF,THE INVENTION It is an object of this inventionto provide a stabilized, uncured, curable, burn resistant, unsaturatedpolyester resin composition having a shelf life of at least about 100days at about 70 C. It is another object to provide two new and novelinhibitors excellently adapted for accomplishing the aforesaid object.Other objects of the invention will be readily apparent to those skilledin the art.

The aforesaid objects have been accomplished by incorporating suchquantity of at least one additive selected from a group consisting of4,6-dinitro-o-cresol or 2,4- dinitroaniline into an uncured, curable,burn resistant, unsaturated polyester resin composition that theinhibitor content of the resulting stabilized polyester resincomposition will [fall within a range of about 0.1-1.5 (or 0.25-1 or0.5-0.8) mole percent.

In general, unsaturated polyester resins are prepared by theesterification of alpha-beta-unsaturated polybasic acids, and dihydricalcohols. Certain compounds of this type can be indicated generically asfollows;

M--GMGMG where, --M- represents an unsaturated dibasic acid moiety and Grepresents a dihydric alcohol moiety.

Modifying dibasic acids may also be used in the polyester resincompositions. Representative dihydric alcohol and unsatuarted polybasicacids are shown below.

In preparing unsaturated polyesters which can be employed in thepractice of the present invention, the alcohol component may compriseethylene glycol, diethylene glycol or propylene glycol, or one ofthegroup of solid polyethylene glycols designated as Carbowax."

Polyethylene glycols such as the Carbowaxes are understood to havemolecular weights above 300-. Those most useful for this invention haveweights below 4000 and preferably are in a range of about 1000 to 2000,e.g., 1500.

The acid component usually comprises an alpha-betaethylenicallyunsaturated polycarboxylic acid such as maleic, furnaric or itaconicacid, or the well-known derivatives of these polycarboxylic acids havingethylenic unsaturation in alpha-beta-relation to a carboxyl group.Polybasic acids such as aconitic acid, tricarballyic acid or citric acidmay also be employed. A plurality of such acids also may be mixed witheach other, if so desired. In many instances, it may be desirable toinclude a modifying dicarboxylic acid free of ethylenic unsaturation.Examples of this latter type of dicarboxylic acid include phthalic acidor terephthalic acid, which, although they contain double bonds in thebenzene ring, do not undergo addition reaction with monomer compoundsand may, therefore, be considered as being the equivalentof saturated.compounds. Likewise, aliphatic dicarboxylic acids such as succinic acid,adipic acid, sebacic acid, or azelaic acid may be substituted for a partof the alpha-beta-ethylenically' unsaturated dicarboxylic acid. Theproportion of the non-ethylene acid with respect to thealpha-beta-ethylenically unsaturated acid is susceptible of widevariation. Halogen-containing (generally saturated) acids are includedto render the cured polymers made by copolymerizing the polyester withstyrene (or the like) burn resistant. These halogen-containing acids aregenerally added in such quantity that the uncured polyester compositionsformed by admixing the polyester with styrene (or a similarethylenically unsaturated monomer) contain about 5-12% bromine or about2030% chlorine. A molecular proportion of 0.25 to 12 moles of saturatedacid per mole of unsaturated acid is usually used for commercialapplications. Also, acid anhydrides of these dicarboxylic acids can beused instead of the dicarboxylic acids.

In preparing the polyester, a small excess (e.g., ca. 5-l0%) of thedihydric alcohol is sometimes employed. The conditions of theesterification reaction are those conventionally employed in preparingpolyester. For example the mixture of the alcohol and the acid is heatedin a vented container or under an inert atmosphere until the water ofreaction is expelled from the system, which usually occurs in atemperature range of about to 210 C. The reaction is continued until theacid value is reduced to a reasonable low point, e.g., within a range ofabout 5 to 50, or until the mixture becomes highly viscous or even solidwhen it is cooled. Usually, these conditions are attained in a period of2 to 20 hours. In any event, the reaction is concluded before theproduct becomes infusible and insoluble because of the advanced stage ofpolymerization. The product is then blended with the ethylenicallyunsaturated monomer in such a manner as to maintain the temperature ofthe blend below about 65 C.

The preferred ethylenically unsaturated monomers for use in preparingthe compositions of this invention are liquid compounds in which thepolyester component is soluble. These monomers contain the C=CH gr0uppreferably with said group attached to a negative radical such as abenzene ring, a chlorine atom, an ester linkage, a nitrile group, or thelike. These ethylenically unsaturated monomers are free of carbon-carbonconjugated double bonds. While many monomers which can be used in thecomposition of our invention will be readily apparent to those skilledin the art, we prefer to use a mem ber selected from a group consistingof styrene, vinyl toluene, u-methylstyrene, dimethylstyrene, themethyl-amethylstyrenes, rx-bromostyrene, B-bromostyrene,a-chlorostyrene, B-chlorostyrene, diallylphthalate, vinyl acetate,methyl methacrylate, and divinyl'benzene.

In general, the ratio of ethylenically unsaturated monomer component (orcomponents Where using at least two such monomers) to the polyestercomponent can vary over a relatively broad range, but, usually, theamount of such monomer is less (on a weight basis) than the amount ofthe polyester component. Usually, the percentage of said monomer willfall within a range of about 10 to 45 percent by weight of the totalmixture of polyester and monomer, and the preferred range of saidmonomer is, in most instances, about 20 to 40 percent.

The polyester resin compositions of this invention contain about 2030%chlorine or about 5-12% bromine and are burn resistant (i.e upon curing(crosslinking between the polyester component and the ethylenicallyunsaturated monomer (e.g., styrene) component of the compositiontheyform copolymers which are very resistant to burning because of theirsubstantial halogen content). The polyesters used in preparing thepolyester compositions of this invention are prepared by esterifyingmixtures of dibasic acids and/or anhydrides with a difunctional glycol.Part of the acid moieties are unsaturated, and the final polyester isdiluted with styrene or the like. The resin for end-use applications iscured with a peroxide catalyst in the presence of a cobalt or similar(e.g., vanadium, iron, or the like) promoter to develop the finalcrosslinked three dimensional thermoset copolymer product.

The curing time of the polyester resin systems varies between about 1minute and about 24 hours. This time span depends, in part, upon suchvariables as type of polyester resin, amount of catalyst, and amount ofinhibitor. The curing temperature of the polyester resin systems variesbetween about C. and about 250 C. Preferably, the polyester resinsystems are cured at room temperature (15 to 35 C.).

As the scope of useful polyester resin systems is extensive, the type ofpromoter which can be used in those systems is also extensive. A fewexemplary promoters are given in the following paragraphs.

One of the promoter types which can be used in the polyester resinsystems is a cobalt salt which is capable of being dissolved in theresinous composition. US. Pat. No. 3,288,735 teaches the use of cobaltsalts, e.g., cobalt naphthenate, to decrease the gelation time ofpolyester resin compositions comprising a polyester resin havingalphabeta-unsaturation, a monomer having an unsaturated bond, andcertain inhibitors. Other cobalt salts excellently adapted for use inpromoters in the compositions of this invention are cobalt octoate orother higher fatty acid salt of cobalt. The amount of cobalt can bevaried from about 0.001 to 0.3 percent calculated as dissolved metalliccobalt based on the total weight of the composition. On the same basis,the preferred amount of cobalt generally ranges from about 0.05 to 0.15percent.

Vanadium promoters disclosed in HS. Pat. No. 3,333,- 021 are useful.Other promoters, including iron, are well known to those skilled in theart.

The promoter can be admixed with the polyester composition before thecomposition is placed in storage or it (the promoter) can be admixedwith the composition at any time before curing the composition.

The polyester resin systems of this invention can also contain othercompatible additives, such as fillers (silica, talc, mica, clay, carbonblack etc.) dyes, reinforcing materials (asbestos, chopped glassfibers), etc.

The resin systems stabilized with agents of this invention are readilycurable, for example, when excess peroxide catalysts and cobalt promoterare employed to destroy, neutralize, or inactivate the inhibitors. Thepreferred catalysts are disclosed in copending application Ser. No.782,734 (Disclosure No. 2693); filed Dec. 10, 1968; D. A. Daniels, R. L.Orem, and E. W. Lard, applicants. For example, the preferred catalystsfor curing the resin systems include a ketone peroxide, such as,Lupersol 224, Lupersol DDM, methylethyl ketone peroxides, and the like,and an organic nonketonic diperoxide, such as Lupersol 256. The amountof each preferred catalyst component must be based on the amount of eachstabilizer present. In general, the non-ketonic diperoxide can bepresent in an amout between about 2 to about 3 percent by weight basedupon the resin composition (polyester plus monomers, etc.) present andthe ketone peroxide can be present in an amount between about 2 to about6 percent by weight based upon the amount of resin components. Theamount of cobalt promoter present is preferably between about 0.05 toabout 0.15 mole percent based on the resin composition.

The instant invention will be better understood by referring to thefollowing specific but nonlimiting examples. It

is understood that said invention is not limited by these,

examples which are offered merely as illustrations; it is alsounderstood that modifications can be made without departing from thespirit and scope of the invention.

EXAMPLES PREPARATION OF RESINS Example 1 Polyester composition A wasprepared by admixing and heating (as hereinbefore described) 10 moles ofdiethylene glycol, 4 moles of maleic anhydride, 5 moles of chlorendicanhydride, 1 mole of adipic acid, 10 moles of styrene, and about 0.02mole of cobalt octoate. There was a total halogen content of about 25percent.

Example 2 Polyester composition B was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 5 moles ofmaleic anhydride, 5 moles of chlorendic anhydride, and 10 moles ofstyrene. There was a total halogen content of about 25 percent. (Acobalt compound, or other catalyst, must be placed in the compositionbefore it can be cured.)

"Example 3 Polyester composition C was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 5 moles ofmaleic anhydride, 5 moles of chlorendic anhydride, 10 moles of styrene,and about 0.02 mole of cobalt octoate. There was a total halogen contentof about 25 percent.

Example 4 Polyester composition D was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 6.2 molesmaleic anhydride, 1.2 moles of tetrabromophthalic anhydride, 2.6 molesof phthalic anhydride and 10 moles of styrene. There was a total halogencontent of about 9 to about 11 percent. (A cobalt compound, or othercatalyst, must be placed in the composition before it can be cured.)

Example 5 Polyester composition E was prepared by admixing and heating(as hereinbefore described) 10 moles of diethylene glycol, 6.2 moles ofmaleic anhydride, 1.2 moles of tetrabromophthalic anhydride, 26 moles ofphthalic anhydride, 10 moles of styrene, and about 0.02 mole of cobaltoctoate. There was a total halogen content of about 9 to about 11percent.

DETERMINATION OF GEL TIME Example 6 We determined the gel time (shelflife) of our polyester resin compositions (with and without the additionof inhibitors) by using the following procedure which is based upon aprocedure published by Cass and Burnett (Ind. Eng. Chem, 1954, 46,16191624).

A sample of polyester resin composition was placed in a test tube havinga diameter of about /2 inch and a height of about 4 inches. Sufficientsample was added to fill the tube within about an inch of its to and acork stopper was inserted tightly into the top of the tubeleaving an aircolumn (bubble) about /2 inch in height between the top of the sampleand the bottom of the stopper. The stoppered tube was immediately placedin an oven at a preselected temperature and examined from time to timeby inverting it (the tube) and noting whether or not the air bubblewould rise when the tube was inverted. The gel point was taken as thepoint at which the bubble ceased to rise when the tube was inverted. Geltime (at the preselected temperature) was the time (hours or days atsaid temperature) required for the sample to reach its gel point.Precision (reproducibility) between runs, as determined by making anumber of runs in duplicate or triplicate, was found to be about :L510%.

Since shelf life (gel time) determinations on the stabilized polyesterresin compositions of this invention would be both tedious and of animpractically long duration if made at 70 C. (because these compositionshave gel times in excess of days at 70 C.), the actual determinationswere made using C. as the above-mentioned preselected temperature. Thethus obtained gel times (gel times at 125 C.) were adjusted to gel timesat 70 C. by using an Arrhenius type relationship set forth in theequation k=Ae which reduces to log E 2.303RT where k=rate ofcrosslinking of the resin at temperature moter; and (e) inhibitors ofthis invention plus a cobalt promoter. These results show thesuperiority of the inhibitors of this invention over conventionalinhibitors.

TABLE II;-GEL TIME, DAYS AI 70 C.

I Polyester 1 Polyester Polyester Polyester Polyester 1 AdditiveComposition A Composition B Composition Composition D Composition ENone. 8 9 6 10 6 0.05 mole percent cobalt octoate 9 8 l0 1 mole percenthydroquinone 2 12 0 35 1 mole percent hydroquinone; 0.05 mole percentobalt octoate 22 30 0.5 mole percent tetrafluorocatecho 05 mole percentcobalt octoate 35 1 mole percent 2, t,(i-tribromocatechol; 0.05 molepercent cobalt octoate- 1 1 mole percent methylhydroquinone 2 I 42 1mole percent methylhydroquinone; 0.05 mole percent cohalt octate. 52 2013 1 mole percent tertiary butylcatechol 2 0 30 1 mole percent tertiarybutylcatechol; 0.05 mole percent cobalt octoate 12 11 10 0.5 molepercent 4,6-dinitro-o-cresol 3 0 200 150 175 165 1 mole percent 2,1-dinitroanilinc 3 7 190 155 150 145 1 In theinstanees of PolyesterResin CompositionsA, C, and "E, Inhibitor of the prior art.

the cobalt in the list of additives includes the 0.05 mole percent ofcobalt added as cobalt octoate where preparing the respective resincompositions. (See Examples 1, 3, and 5, supra.)

gelling) of polyester resin formulations of Examples 1 through 5 whenplotted on semi-log paper (log k vs. 1/ T K.)) each fall on a straightline for the temperature range 70-15 0 C. This straight linerelationship establishes the fact that the mechanism of the gellingreaction does not change over the temperature range of interest, and theslope of the line= E/2.303R, and E, the activation energy of thegelation, can be calculated for each resin.

It is possible to simplify the extrapolation of shelf life of a resincomposition to a temperature other than that at which it was determinedby using a procedure which bypasses calculation of the reaction rate.The change in viscosity which occurs upon aging results fromcrosslinking and conversion of the fluid polyester into a nonflowablegel; this change is substantially constant for each particular polyesterformulation. Therefore, the rate of crosslinking expressed in terms ofrate of change of viscosity (i.e., A viscosity/time) becomes C /timewhere C is a constant. Hence, when log 1/t (where t is time, in days, inwhich gelation occurs) is plotted against 1/T K.), a line is obtainedhaving a slope identical with that of the line represented by a plot of1/ T K.) vs. log k.

It is convenient to plot the colog of 1/t' (or log t itself) vs. 1/ TK.) to obtain a line of the same slope but of opposite sign. Thestraight line obtained by plotting log t vs. 1/ T K.) can beextrapolated to any l/T value required within a range of about 273-4'45K. thus permitting accelerated storage tests based on this use of highertest temperatures. This permits a rapid laboratory determination ofWhether or not an inhibitor prevents setting (gelation) of a polyesterresin composition prior to combination with a catalyst curing system foran end use application.

The following table (Table I) shows the results of 4 tests of gel timemade with polyester resin composition B (a control and 3 runs withinhibitors in varying amounts) v 1 Control, no inhibitor present.

2 Inhibitor present.

The following table (Table II) presents a summary of the resultsobtained in a series of runs using; (a) no inhibitor; (1)) someconventional inhibitors; (c) the inhibitors of this invention; (d)conventional inhibitors plus a cobalt pro- 3 Inhibitor of the instantinvention.

CURING THE STABILIZED POLYESTER RESIN COMPOSITION Example 7 A portion ofpolyester resin composition C which had been stabilized with about 1mole percent 4,6-dinitro-ocresol was admixed with Lupersol 224 andLupersol 256 (these Lupersols are peroxide catalysts, i.e.,polymerization initiators). These materials were admixed in thefollowing proportions; (a) 93.6% stabilized (inhibited) polyester resincomposition; (b) 3.7% Lupersol 224; and (c) 2.7% Lupersol 256. Theresulting mixture was cured by heating to a temperature between 25 C.and 30 C. for 20 minutes. The curing reaction was exothermic andautoaccelerative. The resin system gelled after 20 minutes and the peaktemperature was about 120 C. A well-cured polyester resin was obtained.After 24 hours, the flexural modulus was 200,000 pounds per square inch(p.s.i.).

Example 8 'Example 7 was repeated, except that polyester resincomposition B was used- (the inhibitor was 2,4-dinitroaniline), and 0.02mole percent of cobalt octoate was admixed before curing. A well-curedpolyester resin was ob gained with a flexural modulus of 250,000 p.s.i.after 24 ours.

EXAMPLE 9 An uncured polyester resin system, containing 18.1 weightpercent fiber glass, 3.7 weight percent 3,5-dimethyl-3,5-dihydroxy 1,2peroxycyclopentane solution (30 parts dissolved in 70 parts of propyleneglycol), 2.7 weight percent Lupersol 256, and 74.0 weight percent of thepolyester resin composition A (which was stabilized with 1 mole percent2,4-dinitro-o-cresol), and sufficient additional cobalt octoate to makewas prepared. The aforesaid system was then cured by heating to about40-80 C. The

flexural modulus of the cured material, after H hours was 410,000 p.s.i.

Example 10 Example 9 was repeated, except that the solvent in the1,2-peroxycyclopentane solution was hexylene glycol. A well-cured burnresistant resin was obtained.

Example 11 Example 9 was repeated, except that the solvent in the1,2-peroxycyclopentane solution was a 50/50 mixture of water andhexylene glycol. A well-cured burn resistant resin was obtained.

9 Example 12 Example 9 was repeated, except that the1,2-peroxycyclopentane was replaced with:

l HaC-C-CHz-C-CHa A well-cured burn resistant resin was obtained.

As used herein the term percent unless otherwise defined where used,means parts per hundred by weight.

As used herein the term mole percent (mole percent) means one mole in10,000 grams of resin composition (i.e., one centimole (0.01 mole) perhundred grams of resin composition). Thus, to prepare a resincomposition containing 1 mole percent of 2,4-dinitroaniline one wouldadmix 1 mole (ca. 183 grams) of 2,4-dinitroaniline with enough resincomposition (ca. 9,817 grams) to produce 10,000 grams of inhibited resincomposition.

As used herein the term mole has its generally accepted meaning; i.e., amole of a substance is that quantity of said substance which containsthe same number of molecules of said substance as there are carbon atomsin exactly 12 grams of pure C.

As used herein the term stabilized, uncured, curable, burn resistant,unsaturated polyester resin composition means an unsaturated polyesterwhich; (a) has been admixed with styrene or a similar ethylenicallyunsaturated monomer to form a composition which may or may not contain acobalt or similar accelerator; (b) has been stabilized (had its gel timeextended to at least 100 days at 70 C.) by admixing with a sufficientquantity of at least one of the inhibitors (stabilizers) recited in theabove Summary to make the total inhibitor content of the compositionabout 0.1-1.5 mole percent; (0) has not been cured (i.e., has not beengelled, or polymerized by crosslinking with the styrene (or the like)present therein; and (d) can be cured by treating with a suitableperoxide catalyst (in the presence of a cobalt or other promoter) toyield a burn resistant cross-linked copolymer with the styrene (orsimilar ethylenically unsaturated monomer present in the uncuredcomposition). It will be obvious to those skilled in the art that theuncured composition of this invention will burn where the ethylenicallyunsaturated monomer present therein is styrene or a similar inflammablesubstance. In other words, the term burn resistan as used in thisspecification means that the composition, which may be quite inflammableper se, will, upon curing, yield a burn resistant copolymer.

As used herein the term inhibitor or (stabilizer) means a substance ormixture of substances which will extend the gel time or shelf life(i.e., will retard or prevent the polymerization or crosslinking duringstorage) of the unsaturated polyester and styrene (or otherethylenically unsaturated monomer) which comprise a polyestercomposition.

As used herein the term a soluble cobalt salt means a cobalt salt whichis soluble in a polyester resin composition such as those described inExamples 1-5, supra.

As used herein the expression K. means temperature in degrees Kelvin(i.e., absolute temperature).

Lupersol DDM is a solution comprising 60% methyl ethyl ketone peroxidesand hydroperoxides in dimethyl phthalate. Lupersol 224 is a solutioncomprising 3,5- dimethyl 3,5 dihydroxy-1,2-peroxycyclopentane intriethyl phosphate. Lupersol 256 is a difunctional polyester catalystdesigned especially for elevated temperature applications comprising atleast 90% 2,5-dimethyl-2,5-bis- (Z-ethyl hexanoylperoxy)hexane andhaving at least 6.69 available oxygen.

Burn resistant polymers or copolymers are also called fire retardantpolymers or copolymers.

4,6-dinitro-o-cresol which is also known as Z-methyl- 4,-6-dinitrophenolhas the formula OzN CH;

l lo:

2,4-dinitroani1ine has the formula OzN We claim:

1. A stabilized uncured, curable, burn resistant, unsaturated polyesterresin composition consisting essentially of;

(a) an unsaturated polyester of; (i) a polyhydric alcohol selected froma first group consisting of ethylene glycol, diethylene glycol,propylene glycol, and a polyethylene glycol having a molecular weightbetween 300 and 4000; (ii) a member selected from a second groupconsisting of chlorendic acid and chlorendic anhydride; (iii) a memberselected from a third group consisting of maleic acid, fumaric acid,itaconic acid, and aconitic acid or an anhydride of the third groupmember; and (iv) a member selected from a fourth group consisting oftricarballyic acid, citric acid, succinic acid, adipic acid, sebacicacid, azelaic acid, phthalic acid, and terephthalic acid or an anhydrideof the fourth group member, the chlorine content of the stabilizedpolyester resin composition being 20 to 30%, the mole ratio of the thirdgroup member to the fourth group member being 1:0.25-12;

(b) an ethylenically unsaturated monomer selected from a fifth groupconsisting of styrene, vinyl toluene, u-methylstyrene, dimethylstyrene,the methyl-ocmethylstyrenes, u-bromostyrene, fi-bromostyrene,achlorostyrene, B-chlorostyrene, diallylphthalate, vinyl acetate, methylmethacrylate, and divinylbenzene, the fifth group member constitutingabout 1045% of the stabilized, uncured, curable, burn resistant,unsaturated polyester resin composition; and

(c) an inhibitor selected from a sixth group consisting of4,6-dinitro-o-cresol and 2,4-dinitroaniline, the sixth group memberbeing present in an amount between about 0.1 and about 1.5 mole percentbased on the stabilized, uncured, curable, burn resistant, unsaturatedpolyester resin composition, said composition a gel time of at leastabout days at 2. The composition of claim 1 in which the sixth groupmember is present in an amount between about 0.25 and about 1 molepercent based on the stabilized, uncured, curable, burn resistant,unsaturated polyester resin composition.

3. The composition of claim 1 in which about 0.03 0.5 mole percent ofcobalt, calculated as Co, is present in the stabilized, uncured,curable, burn resistant, unsaturated polyester resin composition, thecobalt being added as a soluble cobalt salt or as an adduct of suchcobalt salt and a member selected from the sixth group, the mole ratioof cobaltzsixth group member in said adduct being about 1:1.

4. The composition of claim 1 in which the fifth group member isstyrene.

12 5. A stabilized, uncured, curable, burn resistant, unrated polyesterresin composition, said composition saturated polyester resincomposition consisting essenhaving a gel time of at least about 100 daysat 70 C. tially of; 6. The composition of claim in which the sixth group(a) an unsaturated polyester of; (i) a polyhydric alcomember is presentin an amount between about 0.25 and hol selected from a first groupconsisting of ethylene 5 about 1 mole percent based on the stabilized,uncured, glycol, diethylene glycol, propylene glycol, and a curable,burn resistant, unsaturated polyester resin compolyethylene glycolhaving a molecular weight beposition. tween 300 and 4000; (ii) a memberselected from a 7. The composition of claim 5 in which about 0.03-0.5second group consisting of tetrabrornophthalic acid mole percent ofcobalt, calculated as 00, is present in and tetrabromophthalicanhydride; (iii) a member the stabilized, uncured, curable, burnresistant, unsatuselected from a third group consisting of maleic acid,rated polyester resin composition, the cobalt being added fumaric acid,itaconic acid, and aconitic acid or an as a soluble cobalt salt or as anadduct of such cobalt anhydride of the third group member; and (iv) asalt and a member selected from the sixth group, the mole memberselected from a fourth group consisting of ratio of cobaltzsixth groupmember in said adduct being tricarballyic acid, citric acid, succinicacid, adipic about 1:1. acid, sebacic acid, azelaic acid, ph'thalicacid, and 3. The C mPOSitiOH of claim 5 in which the fifth groupterephthalic acid or an anhydride of the fourth group ember is styrene.member, the bromine content of said composition References Cited beingabout 5-12%, the mole ratio of the third group member to the fourthgroup member being 1:0.2512; UNITED STATES PATENTS (b) an ethylenicallyunsaturated monomer selected 27797O1 1/1957 Robltschek et a1 154 43 froma fifth group consisting of styrene, vinyl tolu- 3017426 1/1962 Ruffinget 260.4659

ene, a-methylstyrene, dimethylstyrene, the methyl-amethyl-styrene,a-bromostyrene, p-bromostyrene, oc- OTHER REFERENCES chlorostyrene,fi-chlorostyrene, diallylphthalate, vinyl 2 MOIldVal et g Y- 350-52acetate, methyl methacrylate, and divinylbenzene, the Foofd, Chem- 1940,

fifth group member constituting about 1045% of Lang, Chem- & Data 53-56the stabilized, uncured, curable, burn resistant, un- Boenig,Unsaturated y Elsfivief, New York, saturated polyester resincomposition; and 1964 (PP- (c) an inhibitor selected from a sixth groupconsisting of 4,6-dinitro-o-cresol and 2,4-dinitroaniline, the sixthMELVIN GOLDSTEIN Primary Examiner group member being present in anamount between about 0.1 and about 1.5 mole percent based on thestabilized, uncured, curable, burn resistant, unsatu- 260863, DIG. 24

